dax: provide an iomap based fault handler (a7d73fe6) · Commits · 戴 / test

fs/dax.c

+114 −0

Original line number	Diff line number	Diff line
		@@ -1354,4 +1354,118 @@ iomap_dax_rw(struct kiocb iocb, struct iov_iter iter,
		return done ? done : ret;
		}
		EXPORT_SYMBOL_GPL(iomap_dax_rw);

		/**
		* iomap_dax_fault - handle a page fault on a DAX file
		* @vma: The virtual memory area where the fault occurred
		* @vmf: The description of the fault
		* @ops: iomap ops passed from the file system
		*
		* When a page fault occurs, filesystems may call this helper in their fault
		* or mkwrite handler for DAX files. Assumes the caller has done all the
		* necessary locking for the page fault to proceed successfully.
		*/
		int iomap_dax_fault(struct vm_area_struct vma, struct vm_fault vmf,
		struct iomap_ops *ops)
		{
		struct address_space *mapping = vma->vm_file->f_mapping;
		struct inode *inode = mapping->host;
		unsigned long vaddr = (unsigned long)vmf->virtual_address;
		loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
		sector_t sector;
		struct iomap iomap = { 0 };
		unsigned flags = 0;
		int error, major = 0;
		void *entry;

		/*
		* Check whether offset isn't beyond end of file now. Caller is supposed
		* to hold locks serializing us with truncate / punch hole so this is
		* a reliable test.
		*/
		if (pos >= i_size_read(inode))
		return VM_FAULT_SIGBUS;

		entry = grab_mapping_entry(mapping, vmf->pgoff);
		if (IS_ERR(entry)) {
		error = PTR_ERR(entry);
		goto out;
		}

		if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
		flags \|= IOMAP_WRITE;

		/*
		* Note that we don't bother to use iomap_apply here: DAX required
		* the file system block size to be equal the page size, which means
		* that we never have to deal with more than a single extent here.
		*/
		error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
		if (error)
		goto unlock_entry;
		if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
		error = -EIO; /* fs corruption? */
		goto unlock_entry;
		}

		sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);

		if (vmf->cow_page) {
		switch (iomap.type) {
		case IOMAP_HOLE:
		case IOMAP_UNWRITTEN:
		clear_user_highpage(vmf->cow_page, vaddr);
		break;
		case IOMAP_MAPPED:
		error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
		vmf->cow_page, vaddr);
		break;
		default:
		WARN_ON_ONCE(1);
		error = -EIO;
		break;
		}

		if (error)
		goto unlock_entry;
		if (!radix_tree_exceptional_entry(entry)) {
		vmf->page = entry;
		return VM_FAULT_LOCKED;
		}
		vmf->entry = entry;
		return VM_FAULT_DAX_LOCKED;
		}

		switch (iomap.type) {
		case IOMAP_MAPPED:
		if (iomap.flags & IOMAP_F_NEW) {
		count_vm_event(PGMAJFAULT);
		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
		major = VM_FAULT_MAJOR;
		}
		error = dax_insert_mapping(mapping, iomap.bdev, sector,
		PAGE_SIZE, &entry, vma, vmf);
		break;
		case IOMAP_UNWRITTEN:
		case IOMAP_HOLE:
		if (!(vmf->flags & FAULT_FLAG_WRITE))
		return dax_load_hole(mapping, entry, vmf);
		/FALLTHRU/
		default:
		WARN_ON_ONCE(1);
		error = -EIO;
		break;
		}

		unlock_entry:
		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
		out:
		if (error == -ENOMEM)
		return VM_FAULT_OOM \| major;
		/* -EBUSY is fine, somebody else faulted on the same PTE */
		if (error < 0 && error != -EBUSY)
		return VM_FAULT_SIGBUS \| major;
		return VM_FAULT_NOPAGE \| major;
		}
		EXPORT_SYMBOL_GPL(iomap_dax_fault);
		#endif /* CONFIG_FS_IOMAP */

include/linux/dax.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,8 @@ ssize_t dax_do_io(struct kiocb , struct inode , struct iov_iter *,
		get_block_t, dio_iodone_t, int flags);
		int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
		int dax_truncate_page(struct inode *, loff_t from, get_block_t);
		int iomap_dax_fault(struct vm_area_struct vma, struct vm_fault vmf,
		struct iomap_ops *ops);
		int dax_fault(struct vm_area_struct , struct vm_fault , get_block_t);
		int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
		void dax_wake_mapping_entry_waiter(struct address_space *mapping,

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